bg-image($url)
  background-image url($url + "@2x.png")
  @media (-webkit-min-device-pixel-ratio: 3), (min-device-pixel-ratio: 3)
    background-image url($url + "@3x.png")
border-1px($color)
    position relative
    &:after
        display block
        position absolute
        left 0
        bottom 0
        width 100%
        border-top 1px solid $color
        transform: scale(0.5)
        transform-origin: 0 100%
        content:''
